Linkage type rear suspension system for a motor vehicle



Nov. 8, 1966 w. D. ALLISON 3,284,095

LINKAGE TYPE REAR SUSPENSION SYSTEM FOR A MOTOR VEHICLE Original FiledDec. 18, 1964 2 Sheets-Sheet 1 F'IG.

WILLIAM D. ALLISON lNI/ENTOR }.A MM

A T TOR/VEVS Nov. 8, 1966 D. ALLISON 3, 5

W LINKAGE TYPE REAR SUSPENSION SYSTEM FOR A MOTOR VEHICLE Original FiledDec. 18, 1964 2 SheetsSheet 2 FIG. 2

WILLIAM D. ALLISON INVENTOP A TTORNEVS I IO United States Patent3,284,095 LINKAGE TYPE REAR SUSPENSION SYSTEM FOR A MOTOR VEHICLEWilliam D. Allison, Grosse Pointe Farms, Mich, assignor to Ford MotorCompany, Dearborn, Mich, a corporation of Delaware Continuation ofapplication Ser. No. 419,483, Dec. 18, 1964. This application Apr. 1,1966, Ser. No. 544,654 17 Claims. (Cl. 280-424) This application is acontinuation of my copending application Serial Number 419,483, filedDecember 18, 1964 and entitled Linkage Type Rear Suspension Systern fora Motor Vehicle.

The present invention is generally related to rear suspension systemsfor motor vehicles, and more particularly to a rear suspension system ofthe linkage type.

It is the basic object of any motor vehicle suspension system toresiliently support the vehicle body upon the wheels and to isolate roadirregularities from the passenger compartment. In addition, a superiorvehicle suspension system should provide a soft boulevard ride, havegood road holding qualities while cornering, and isolate noise andvibration from the vehicle body.

These features are not always compatible. In a conventional suspensionstructure, a soft ride usually leads to instability at high vehiclespeeds or loss of precise cornering control. Similarly, a suspensionsystem having exceptional vehicle control characteristics is usuallyaccompanied by a harsh ride.

Therefore, it is the principal object of the present invention toprovide a superior vehicle suspension system of the linkage type whichcombines these desirable operating characteristics.

It is a further object of the present invention to provide a rearsuspension system that is so arranged that when a side force is appliedto the sprung mass, the rear of the vehicle is displaced sidewaysrelative to the rear axle. This lateral displacement is known in the artas lateral compliance. Lateral compliance is desirable because itreduces ride harshness and side shake.

It is another object of the present invention to provide a pair ofsuspension arms or links that extend forwardly and outwardly in adiverging relationship from the axle housing to their attachments withthe body so that lateral displacement of the body is accompanied by acanting of the axle in the direction of understeer.

It is still another object of the invention to provide a torque armwhich interconnects the axle housing and the vehicle body. In accordancewith the preferred embodiment of the present invention, the torque armis connected to the axle housing by a resilient means which permitslateral displacement of the body relative to the axle. The torque armprevents rotation of the axle during acceleration and braking. In asuspension of the present invention, the torque reaction is handledsolely by the torque arm and is isolated from the other suspension armsand links.

Another object of the present invention is to connect the forward end ofthe torque arm to the vehicle body by a shackle device so that thetorque arm cannot be loaded in either compression or tension duringacceleration and braking. The diverging suspension arms carry all of thebraking and accelerating forces while the torque arm acts as the soletorque reaction member to prevent rotation of the axle housing.

The many objects and advantages of the present invention will becomeamply apparent upon eonsideraton of the following discussion and theaccompanying drawings in which:

FIGURE 1 is a perspective view of a vehicle rear suspension system ofthe linkage type constructed in accordance with the present invention,and

FIGURE 2 is a top plan view of the suspension of FIGURE 1.

Referring now to the drawings wherein the presently preferred embodimentis illustrated, FIGURE 1 discloses a vehicle frame 10 which is comprisedof left and right side rails 12 and 14. The side rails 12, 14 areinterconnected at their rear ends by a cross frame member 16 and at apoint forwardly of member 16 by a second cross frame member 18.

An axle housing 20 rotatably supports a left and a right road wheel 22and 24 at its outer ends. The axle housing 20 has a differential housing26 that is centrally located. Housing 26 contains gearing fordistributing torque through axle shafts contained within the axlehousing 20. The axle shafts drive the road wheels 22 and 24.

Suspension means are provided to interconnect the axle housing 20 andthe frame 10. In accordance with the present invention, the suspensionmeans comprise left and right suspension links 28 and 30. The suspensionlinks are arranged in a generally forwardly and outwardly divergingrelationship. The left link 28 is formed of leaf spring steel and has acentral portion 32 that is arranged in a vertical plane. At the ends ofthe left link 28, leaf spring eyes 34 and 36 are formed. The eyes 34 and36 have generally transverse pivot axes. Rubber bushings are positionedwithin the eyes 34 and 36 and are indicated by the reference numerals 38and 40. A bracket 42 is connected to the left frame rail 12 and is usedto pivotally support, by the means of a pivot bolt 44, the eye 34 andthe forward end of the left link 28. A bracket 46 is welded to the outerleft-hand end of the axle housing 20 which pivotally supports thebushing 40 within the eye 36 by means of a pivot bolt 48.

The construction and connection of the right-hand suspension link 30 isgenerally similar. The rear end of the link 30 is formed into an eye 50which contains a bushing 52 and is pivotally connected to an axlehousing bracket 54 by means of a pivot bolt 56. A forward bracket 58 issecured to the frame side rail 14 and is connected to an eye 60 formedat the forward end of the link 30. A bushing 62 is disposed within theeye 60 and is pivotally connected to a pivot bolt 64. The leaf springlink 30 also has a vertically arranged centrally situated sectionbetween the eyes 50 and 60. This section is indicated by the referencenumeral 66.

A pair of brackets 68 and 70 are welded or otherwise secured to theframe cross member 18. These brackets have depending portions that areadapted to engage hairpin-shaped torsion bars 72 and 74. Left bar 72 isprovided with an upstanding right angle end portion 76 which has itsupper end extending through an opening 78 in the bracket 68. Near thebend of the angled end portion 76, a reaction member 80 is secured tothe bracket 68. The bar has a torsional portion 82 which extendsforwardly from the angled end 76. The bar 72 then doubles back to form asecond torsional portion 84. The end of the torsional portion 84 isoutwardly formed into an angled load lever arm 86.

A fitting 88 is secured to the angled end 86 of the bar 72 near itsconnection with the torsional portion 84. The fitting 88 is pivotallyconnected to a bolt 90 that is secured to the lower end of the bracket63. The laterally outer end of the angled arm 86 is connected to thestud portion of a ball and socket joint 92. The socket portion of thatjoint is secured to the portion 32 of left spring suspension link 28 bya pair of special bolts 94.

The angled ends '76 and 86 of the torsion bar 72 constitute load leverarms for transferring spring load from the chassis bracket 68 to thesuspension arm 28.

Right torsion bar 74 is similarly arranged and connected. Bar 74 has anangled end portion 96 that is secured within the bracket 70 and isintegrally connected "D 6) to a torsional segment 98. The bar 74 doublesback on the torsional segment 98 to form a second torsional segment 100.A laterally extending load lever arm 102 is integrally connected to theend of the torsional segment 100. The outer end of the lever arm 102 isconnected to the vertically arranged portion 66 of the spring suspensionlink 30 by the means of a ball joint 104. The inner end of the lever armportion 102 is pivotally connected to the bracket 70 by means of aspecial fitting similar in construction to left-hand fitting 88 that ispivotally connected to the bracket 68.

A torque arm 106 is provided to prevent rotation of the axle housing 20.The torque arm 106 has a forward end 108 that is connected to anextension 110 from the side rail 14 by means of a shackle 112. A bracket114 is welded to the axle housing 20 and supports vertically spacedapart resilient bushings 116 and 118. These bushings are connected, inturn, to the rear end of the torque arm 106. It is noted that the torquearm 106 has a bifurcated end construction for attachments to thebushings 116 and 118.

The rear suspension is arranged so that when a side force is applied tothe sprung mass, the rear of the vehicle body is displaced sidewaysrelative to the rear axle 20. This lateral displacement is permitted bythe resilient flexibility of the spring metal links 28 and 30 whichinterconnect the axle housing and the frame. Since the front of the bodydoes not move laterally, the body undergoes angular rotation about avertical axis through the center of the front tread. Each point on thesprung mass rotates about this axis in proportion to its distance fromthe axis and the amount of lateral displacement or compliance at therear suspension.

This lateral displacement of the sprung mass at the rear axle isutilized to effect a steering movement of the rear axle 20 in adirection to oppose the side force. The steering of the rear axle 20 isaccomplished by the angular placement of the two spaced spring metalsuspension links 20, 30 connecting the axle 20 to the frame 10. As theframe pivots 44, 64 of the suspension links 28, 30 rotate around thevertical front axis, the pivot on one side of the car goes forward andout, and the opposite pivot moves in and rearwardly relative to thecenter of the rear axle 20. The fixed length of each suspension link 28and 30 imparts a steering movement to the rear axle 20 according to thespacing and angular positions of the links 28 and 30.

Inasmuch as the steering movement applied to the rear axle 20 is in adirection to oppose the side force, it is considered to be in thedirection of understeer. The understeering produced by lateralcompliance is proportional to the lateral force and is not appreciablyeffective by vehicle ride height in contrast to the pronounced effect ofride height on the rear axle steer produced by body roll.

In addition to providing a means of obtaining rear suspensionundersteering that is insensitive to ride height,

' lateral compliance provides other benefits in the forms of increasedroad holding on corners and a reduction in side shake. In a solid axlerear suspension system, individual vertical movement of either rearwheel imparts a sideways push to the sprung mass at the roll center. Theapplication of lateral forces to the body produces noise, vibration andside shake. Lateral compliance or flexibility between the sprung massand the rear axle permits the axle to follow road irregularities with asubstantial reduction in the magnitude lateral forces between the bodyand axle in comparison with the conventional rear suspension. The neteffect on the body is a pronounced reduction in noise, vibration andharshness. The net effect on the axle is a greatly increased traction oncorners due to the diminished peak side forces applied to the tires.

The foregoing description constitutes the presently preferred embodimentof this invention. Modifications and alterations may occur to thoseskilled in the art which will come within the scope and spirit of thefollowing claims.

I claim.

1. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a forwardly andoutwardly diverging relationship, said suspension links being formed ofleaf spring material and having laterally resilient spring portions, apair of left and right brackets secured to said frame adjacent to saidlinks, a pair of left and right U-shaped torsion bars, each of said barshaving one lever arm end secured to a bracket and another portionpivotally connected to the same bracket, said torsion bars each having alaterally extending lever arm portion connected to a suspension link, aball and socket joint interconnecting the ends of said laterallyextending lever arms and said suspension links, a torque arminterconnecting said axle and said frame, mean-s connecting one end ofsaid torque arm to said axle and constructed to permit lateraldisplacement of said axle relative to said frame while at the same timeresisting rotation of said axle about its own axis, said meanscomprising a bracket secured to said axle and having vertically spacedapart resilient bushings, said one end of said torque arm beingconnected to said spaced apart bushings, means connect- 7 ing the otherend of said torque arm to said frame and constructed to permit saidother end to be displaced longitudinally while resisting verticaldisplacement of said other end relative to said frame, said meanscomprising a shackle pivotally connected to said frame at one of itsends and pivotally connected to said torque arm at the other of itsends, said suspension means permitting said vehicle frame to movelaterally with respect to said axle whereby one end of said axle ismoved forwardly and the other end of said axle is moved rearwardly toprovide an understeer eifect.

2. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a forwardly andoutwardly diverging relationship, a pair of left and right bracketssecured to said frame adjacent to said links, a pair of left and rightU-shaped torsion bars, each of said bars having one lever arm endsecured to a bracket and another portion pivotally connected to the samebracket, said torsion bars each having a laterally extending lever armportion connected to a suspension link, a torque arm interconecting saidaxle and said frame, means connecting one end of said torque arm to saidaxle and constructed to permit lateral displacement of said axlerelative to said frame while at the same time resisting rotation of saidax-le about its own axis, said means comprising a bracket secured tosaid axle and having vertically spaced apart resilient bushings, saidone end of said torque arm being connected to said spaced apartbushings, means connecting the other end of said torque arm to saidframe and constructed to permit said other end to 'be displacedlongitudinally while resisting vertical displacement of said other endrelative to said frame, said means comprising a shackle pivotallyconnected to said frame at one of its ends and pivotally connected tosaid torque arm at the other of its ends, said suspension meanspermitting said vehicle frame to move laterally with respect to saidaxle whereby one end of said axle is moved forwardly and the other endof said axle is moved rearwardly to provide an understeer effect.

3. A vehicle frame, a vehicle axle, suspension means inter-connectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a forwardly andoutwardly diverging relationship, said suspension links being formed ofleaf spring material and having laterally resilient spring portions, apair of left and right brackets secured to said frame adjacent to saidlinks, a pair of left and right U-shaped torsion bars, each of said barshaving one lever arm end secured to a bracket and another portionpivotally connected to the same bracket, said torsion bars each having alaterally extending lever arm portion connected to a suspension link, atorque arm interconnecting said axle and said frame, means connectingone end of said torque arm to said axle and constructed to permitlateral displacement of said axle relative to said frame while at thesame time resisting rotation of said axle about its own axis, meansconnecting the other end of said torque arm to said frame andconstructed to permit said other end to be displaced longitudinallywhile resisting vertical displacement of said other end relative to saidframe, said means comprising a shackle pivotally connected to said frameat one of its ends and pivotally connected to said torque arm at theother of its ends, said suspension means permitting said vehicle frameto move laterally with respect to said axle whereby one end of said axleis moved forwardly and the other end of said axle is moved rearwardly toprovide an understeer effect.

4. A vehicle frame, a vehicle axle, suspension means interconecting saidaxle and said frame, said suspension means comprise a pair of left andright suspension links each having one of their ends pivotally connectedto said axle and the other of their ends pivotally connected to saidframe, said suspension links being arranged in a forwardly and outwardlydiverging relationship, said suspension links being formed of leafspring material and having laterally resilient spring portions, a pairof left and right brackets secured to said frame adjacent to said links,a pair of left and right U-shaped torsion bars, each of said bars havingone lever arm end secured to a bracket and another portion pivotallyconnected to the same bracket, said torsion bars each having a laterallyextending lever arm portion connected to a suspension link, a torque arminterconnecting said axle and said frame, means connecting one end ofsaid torque arm to said axle and constructed to permit lateraldisplacement of said axle relative to said frame while at the same timeresist-ing rotation of said axle about its own axis, means connectingthe other end of said :torque arm to said frame and constructed topermit said other end to be displaced longitudinally while resistingvertical displacement of said other end relative to said frame, saidsuspension means permitting said vehicle frame to move laterally withrespect to said axle whereby one end of said axle is moved forwardly andthe other end of said axle is moved rear- Wardly to provide anundersteer effiect.

5. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a forwardly andoutwardly diverging relationship, said suspension links being formed ofleaf spring material and having laterally resilient spring portions, apair of left and right brackets secured to said frame adjacent to saidlinks, a pair of left and right U-shaped torsion bars, each of said barshaving one lever arm end secured to a bracket and another portionpivotally connected to the same bracket, said torsion bars each having alaterally extending lever arm portion connected to a suspension link, atorque arm interconnecting said axle and said frame, said suspensionmeans permitting said vehicle frame to move laterally with respect tosaid axle housing whereby one end of said axle housing is movedforwardly and the other end of said axle housing is moved rearwardly toprovide an understeer effect.

6. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a forwardly andoutwardly diver-sing relationship, said suspension links havinglaterally resilient spring portions, 21 pair of left and right U-shapedtorsion bars, each of said bars having one lever arm end secured to saidframe and a laterally extending lever arm portion connected to asuspension link, a torque arm interconnecting said axle and said frame,means connecting one end of said torque arm to said axle and constructedto permit lateral displacement of said axle relative to said frame whileat the same time resisting rotation of said axle about its own axis,means connecting the other end of said torque arm to said frame andconstructed to permit said other end to be displaced longitudinallywhile resisting vertical displacement of said other end relative to saidframe, said suspension means permitting said vehicle frame to movelaterally with, re spect to said axle whereby one end of said axle ismoved forwardly and the other end of said axle is moved rearwardly toprovide an understeer effect.

7. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being formed of leaf springmaterial and having laterally resilient spring portions, a pair ofU-shaped torsion bars each having one lever arm end secured to saidframe and another lever arm end connected to a suspension link, a torquearm interconnecting said axle and said frame, means connecting one endof said torque arm to said axle constructed to permit lateraldisplacement of said axle relative to, said frame while at the same timeresisting rotation of said axle about its own axis, means connecting theother end of said torque arm to said frame constructed to permit saidother end to be displaced longitudinally While resisting verticaldisplacement of said other end relative to said frame.

8. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being formed of leaf springmaterial and having laterally resilient spring portion-s, a pair ofU-shaped torsion bars each having one lever arm end secured to saidframe and another end connected to a suspension link, a torque arminterconnecting said axle and said frame.

I 9. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being formed of leaf springmaterial and having laterally resilient spring portions, a pair ofU-shaped torsion bars each having one lever arm end secured to saidframe and another lever arm end connected to a suspension link, a balland socket joint interconnecting the end of said last mentioned leverarm and said suspension link, a torque arm interconnecting said axle andsaid frame.

10. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being arranged in a for wardly andoutwardly diverging relationship, said suspension links having laterallyresilient spring portions, suspension Spring means constructed tosupport said frame on said axle and said wheels, a torque arminterconnecting said axle and said frame, means connecting one end ofsaid torque arm to said axle and constructed to permit lateraldisplacement of said axle relative to said frame While at the same timeresisting rotation of said axle about its own axis, means connecting theother end of said torque arm to said frame and constructed to permitsaid other end to be displaced longitudinally While resisting verticaldisplacement of said other end relative to said frame, said suspensionmeans permitting said vehicle frame to move laterally with respect tosaid axle whereby one end of said axle is moved forwardly and the otherend of said axle is moved rearwa'rdly to provide an nndersteer effect.

11. The combination of claim 10 and including said suspension springmeans comprising a pair of torsion springs each having one end connectedto said frame and another end connected to a suspension link.

12. A vehicle frame, a vehicle axle, suspesion means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, said suspension links being formed of leaf springmaterial and having laterally resilient spring portions, suspensionspring means constructed to support said frame on said axle and saidWheels, a torque arm interconnecting said axle and said frame, meansconnecting one end of said torque arm to said axle constructed to permitlateral displacement of said axle relative to said frame While at thesame time resisting rotation of said axle about its own axis, meansconnecting the other end of said torque arm to said frame constructed topermit said other end to be displaced longitudinally w'hile resistingvertical displacement of said other end relative to said frame.

13. The combination of claim 12 and including said suspension springmeans comprising a pair of torsion 0 m springs each having one endconnected to said frame and another end connected to a suspension link.

14. A vehicle frame, a vehicle axle, a road wheel rotatably mounted ateach of the ends of said axle, suspension means interconnecting saidaxle and said frame, said suspension means comprise a pair of left andright suspension links each having one of their ends pivotally connectedto said axle and the other of their ends pivotally connected to saidframe, said suspension links being formed of leaf spring material andhaving laterally resilient spring portions, suspension spring meansconstructed to support said frame on said axle and said wheels, asuspension arm interconnecting said axle and said frame.

15. The combination of claim 14 and including said suspension springmeans comprising a pair of torsion springs each having one end connectedto said frame and another end connected to a suspension link.

16. The combination of claim 15 and including a ball and socket jointinterconnecting said other torsion spring end and said suspension link.

17. A vehicle frame, a vehicle axle, suspension means interconnectingsaid axle and said frame, said suspension means comprise a pair of leftand right suspension links each having one of their ends pivotallyconnected to said axle and the other of their ends pivotally connectedto said frame, a pair of left and right brackets secured to said frameadjacent to said links, a pair of left and right U-shaped torsionsprings, each of said springs having one end secured to a bracket andanother portion pivotally connected to the same bracket, the end of saidother portion being connected to a suspension link, a suspension arminterconnecting said axle and said frame.

References Cited by the Examiner UNITED STATES PATENTS 3,002,580 10/1961Mueller et al. 18073 3,029,091 4/1962 Allison 280-124 3,205,967 9/1965Stotz et al l73 BENJAMIN HERSH, Primary Examiner.

M. S. SALES, Assistant Examiner.

1. A VEHICLE FRAME, A VEHICLE AXLE, SUSPENSION MEANS INTERCONNECTINGSAID AXLE AND SAID FRAME, SAID SUSPENSION MEANS COMPRISE A PAIR OF LEFTAND RIGHT SUSPENSION LINKS EACH HAVING ONE OF THEIR ENDS PIVOTALLYCONNECTED TO SAID AXLE AND THE OTHER OF THEIR ENDS PIVOTALLY CONNECTEDTO SAID FRAME, SAID SUSPENSION LINKS BEING ARRANGED IN A FORWARDLY ANDOUTWARDLY DIVERGING RELATIONSHIP, SAID SUSPENSION LINKS BEING FORMED OFLEAF SPRING MATERIAL AND HAVING LATERALLY RESILIENT SPRING PORTIONS, APAIR OF LEFT AND RIGHT BRACKETS SECURED TO SAID FRAME ADJACENT TO SAIDLINKS, A PAIR OF LEFT AND RIGHT U-SHAPED TORSION BARS, EACH OF SAID BARSHAVING ONE LEVER ARM END SECURED TO A BRACKET AND ANOTHER PORTIONPIVOTALLY CONNECTED TO THE SAME BRACKET, SAID TORSION BARS EACH HAVING ALATERALLY EXTENDING LEVER ARM PORTION CONNECTED TO A SUSPENSION LINK, ABALL AND SOCKET JOINT INTERCONNECTING THE ENDS OF SAID LATERALLYEXTENDING LEVER ARMS AND SAID SUSPENSION LINKS, A TORQUE ARMINTERCONNECTING SAID AXLE AND SAID FRAME, MEANS CONNECTING ONE END OFSAID TORQUE ARM TO SAID AXLE AND CONSTRUCTED TO PERMIT LATERALDISPLACEMENT OF SAID AXLE RELATIVE TO SAID FRAME WHILE AT THE SAME TIMERESISTING ROTATION OF SAID AXLE ABOUT ITS OWN AXIS, AND MEANS COMPRISINGA BRACKET SECURED TO SAID AXLE AND HAVING VERTICALLY SPACED APARTRESILIENT BUSHINGS, SAID ONE END OF SAID TORQUE ARM BEING CONNECTED TOSAID SPACED APART BUSHINGS, MEANS CONNECTING THE OTHER END OF SAIDTORQUE ARM TO SAID FRAME AND CONSTRUCTED TO PERMIT SAID OTHER END TO BEDISPLACED LONGITUDINALLY WHILE RESISTING VERTICAL DISPLACEMENT OF SAIDOTHER END RELATIVE TO SAID FRAME, SAID MEANS COMPRISING A SHACKLEPIVOTALLY CONNECTED TO SAID FRAME AT ONE OF ITS ENDS AND PIVOTALLYCONNECTED TO SAID TORQUE ARM AT THE OTHER OF ITS ENDS, SAID SUSPENSIONMEANS PERMITTING SAID VEHICLE FRAME TO MOVE LATERALLY WITH RESPECT TOSAID AXLE WHEREBY ONE END OF SAID AXLE IS MOVED FORWARDLY AND THE OTHEREND OF SAID AXLE IS MOVED REARWARDLY TO PROVIDE AN UNDERSTEER EFFECT.